A title does not a theme make.

: You are correct
: in that the Chief has no political power on his own, but he's also

zip

No power. No potency. No potential for action.

: all while being one of the most lethal living things in the universe,

He was one of the most lethal living things in the universe. That was back when he was the tip of the spear for Humanity, with all the resources and manpower and mobility of the UNSC supporting him. Back when he had specialists dedicated to maintaining his armor and gathering intel for the operations that they sent him on.

: AND
: having been given the geas by the Librarian,

That and $4.50 will get him a cappuccino at Starbucks.

: which we still don't know
: what else had it done to him, but in cut dialogue the Librarian told him
: to guide humanity.

How does he guide us? How can he go from being a soldier to a leader of a divided humanity? What qualifies him to take that role? Are humans geassed into following him? If they are, shouldn't his priority be finding the figurative Lot 192 for the Librarian's W-Y-K gene?

: In any case, a modern golem that turns rogue would not
: be something people would like,

In any case, all the right people have to do is reach out and wipe the aleph from its forehead. Or whatever the modern equivalent is.